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Mossberg 590 Shockwave

• easy
• Shop tier 1
• medium confidence
• Shotgun
• pump action
• birds head grip
• tube magazine
• tang safety
• special legal status

field strip ~3 min · reassembly ~5 min · detail strip ~25 min

Specifications

Model-specific safety

• The Shockwave has a bird’s-head grip and no shoulder stock. It is NOT designed to be fired from the shoulder, and its recoil with full-power 12 gauge loads is substantial and directed into the wrist. Learn the correct hold before firing it.
• The strap on the forend exists to keep your support hand behind the muzzle. Use it. Hand-over-muzzle injuries are the characteristic accident with short pump shotguns.
• This firearm has a specific legal status in the United States: it is not a shotgun and not a pistol, but a "firearm" by overall length and the fact it was never fitted with a stock. ADDING A STOCK to it creates a short-barrelled shotgun, which is a regulated configuration. Do not fit a stock.
• Unloading a tube magazine takes several cycles. Verify both the chamber and the tube.
• The tang safety sits on top of the receiver.

Under spring tension

• Magazine tube spring and follower
• Hammer spring

Easily lost parts

Trigger housing pin · Magazine cap · Cartridge stops · Bolt slide

Tools

Shop difficulty

Shop tier 1 Tier 1 — easy among shotguns, for the full job: strip to the parts that get coated and put it back together working. The shortest list in the category (34 items) on the 500/590 action; nothing held under tension while a pin goes in. Same alignment traps as the 500 (bolt slide and action bars, shell stop and interrupter) and the 590 magazine spring retainer.

Parts: 34 numbered parts (Shockwave exploded-view parts list shared by the 500 and 590 Shockwave (rows 1 and 4 are 500-only, 7 and 8 are 590-only); trigger housing and bolt listed as assemblies), from Owners Manual for 500 and 590 Shockwave and Compact Cruiser (doc 103855) — O.F. Mossberg & Sons, Inc., p. 30–31 resources.mossberg.com [2].

Bench time: about 30 min to strip, 45 min to rebuild (estimate). As Model 500 (Shockwave list is short); rebuild longer for bolt-slide/action-bar alignment and the 590 magazine spring.

Small parts: 1 pins, 1 springs, 0 detents or plungers (counted from the manufacturer's parts list (one per key number unless a quantity is given))

What comes off for coating

• Barrel and magazine: barrel (takedown screw or magazine cap), magazine spring retainer, spring and follower, magazine tube from receiver (optional) — strap wrench, padded vise
• Forend / action slide: action slide tube nut, forend, anti-rattle spring — tube nut tool
• Receiver: trigger housing pin and trigger housing, elevator, cartridge stop and interrupter, bolt and bolt slide, ejector and ejector screw, safety button screw, safety button, detent plate, detent ball and spring
• Bolt: bolt lock pin and bolt lock, extractor pins, extractors and springs, firing pin retaining pin, firing pin, washer and spring
• Trigger housing: hammer, trigger, sear and disconnector group on their pins (only if the housing itself is being coated; Mossberg advises
• Stock / grip: recoil pad screws and pad, stock bolt, lock washer and washer — long 1/2 in. or 13 mm socket on extension

Special tools

• Tube nut tool — Forend action slide tube nut
• Strap wrench and padded vise — Magazine tube off the receiver
• Long socket extension — Stock bolt deep in the buttstock
• Roll/pin punches 1/16-1/8 in. — Bolt extractor and firing pin pins

Known pain points

• The bolt, bolt slide and both action slide bars have to go back in the same relationship they came out; a bar out of its cut or a bolt slide offered at the wrong point of forend travel will not drop in or binds the action. (reassembly)
  Source: Owners Manual for 500 and 590 Shockwave and Compact Cruiser (doc 103855) — O.F. Mossberg & Sons, Inc. resources.mossberg.com [2] — “Pay special attention to the position of the bolt, bolt slide and action slide bar assembly during this portion of the disassembly, as the parts must be in the same relationship during reassembly.”
• On 590-pattern guns the magazine spring retainer and spring are under significant pressure when the cap comes off or goes back on. (both)
  Source: Owners Manual for 500 and 590 Shockwave and Compact Cruiser (doc 103855) — O.F. Mossberg & Sons, Inc. resources.mossberg.com [2] — “Model magazine spring retainers and springs are under significant spring pressure. Use caution to prevent injury”
• Owners report the shell stop and interrupter get jammed in wrong and the action bars mis-seated when the gun is forced together; it only runs once everything lines up. (reassembly)
  Owners report: Seeking help from someone who owns a Mossberg 500 in the Bay Area — Calguns.net calguns.net [3] — “mossbergs are great but they can be harder to put back together. it sounds like the action bars are not in the right spot. also i will bet the shell stop and interrupter are jammed in wrong.”
• The hammer must be at full cock to get the trigger housing back in, and the safety must be on to reinstall the bolt; neither is obvious and forcing it damages parts. (reassembly)
  Source: The Mossberg Model 500: History & Disassembly — American Rifleman (NRA) americanrifleman.org [4] — “Be aware that the hammer must be in the full-cock position for reinsertion of the trigger assembly and that the safety must be in the “on” position to re-install the bolt assembly.”

Fit or check on rebuild

• Magazine tube torqued and aligned to the barrel lug — Tube carries the barrel; it is refitted hand-tight-plus with a strap wrench and must line up with the takedown screw or cap.
  Source: TM 9-1005-338-13&P — Department of the Army archive.org [5] — “Place strap style pipe wrench around magazine tube assembly (2) and turn to the left (counterclockwise),”
• Safety detent feel — The tang safety's ball and spring under the detent plate set the click; a missing ball gives a loose safety.
• Function check: safety, trigger/sear release, disconnector and feeding with dummy rounds — Standard after any detail strip; a mis-assembled sear or disconnector can double or fail to fire.

This is Pew-Takedown's rating, not the manufacturer's. How tiers are rated. Forum reports are owners' experience, not specifications.

Manufacturer videos

Official videos from O.F. Mossberg & Sons's own channels, linked rather than copied. Where a video and the steps on this page differ, follow the manufacturer's manual and video.

• Loading and Unloading - Mossberg 500 / 590 Series Shotguns MOSSBERG clearing, operation · 2020-05-12
  Covers: Mossberg 500 / 590 series pump-action shotguns. Mossberg markets the Shockwave as the '590 Shockwave', but the video does not name it.
• How Mossberg 500/590 Pump-Action Shotguns Work MOSSBERG operation · 2024-06-18
  Covers: Mossberg 500 and 590 pump-action shotguns (per description). The Shockwave is a 590-family pump, but the video does not name it.

Procedures

Torque specifications

No sourced torque values from the manufacturer are recorded for this firearm. Where a fastener has a specified torque — action screws, scope bases, muzzle devices, barrel nuts — get it from the manufacturer or a gunsmith rather than estimating it.

What the manufacturer does say: The manufacturer's documents give no torque value. They say: "With a 1/4” allen head wrench attach the Raptor Grip to the receiver by tightening the socket head cap screw as seen in Figure 28." (Owners Manual for 500 and 590 Shockwave and Compact Cruiser (doc 103855), PDF p. 19) "Slide the barrel into the receiver and tighten the magazine cap, finger tight only. DO NOT use pliers or a wrench to tighten magazine cap." (Owners Manual for 500 and 590 Shockwave and Compact Cruiser (doc 103855), PDF p. 7)

Parts list

Transcribed from the manufacturer's parts list (Owners Manual for 500 and 590 Shockwave and Compact Cruiser (doc 103855) — O.F. Mossberg & Sons, Inc., p. 30–31 resources.mossberg.com [2]) — "EXPLODED VIEW PARTS LIST, SHOCKWAVE®", shared by the 500 and 590 Shockwave. Rows 1 and 4 are 500-only; 7 and 8 are 590-only. The Compact Cruiser list (pp. 28–29) is left out. No part numbers.. Key numbers refer to the exploded view in that document.

Function check

• Verify the shotgun is unloaded — chamber and magazine tube — before each step.
• Cycle the action fully and confirm it locks closed.
• With the hammer cocked, engage the safety and press the trigger. The hammer must not fall.
• Disengage the safety and press the trigger. The hammer should fall.
• With the hammer down, confirm the action will not open until the action release is pressed.
• Load two dummy shells into the magazine and confirm they feed and eject one at a time.
• Confirm the forend strap is intact and secure — it is what keeps your hand behind the muzzle.

Maintenance

Lubrication points

• Action bars in their receiver grooves
• Bolt body and locking lug
• Magazine tube exterior
• Hammer and sear pivots

Cleaning notes

Keep the magazine tube interior clean and dry rather than oiled — oil there collects plastic wad residue and slows the follower.

Suggested inspection interval: roughly every 1000 rounds. This is a general guideline, not a manufacturer specification.

Wear parts to inspect

Extractor · Shell latches · Magazine spring · Action bars

Common issues

Also covers

The procedures above are reported to apply to: Mossberg 590 Shockwave in 12 gauge, 20 gauge, and .410 · Remington TAC-14 (similar configuration on an 870 action). Verify against the manual for your specific model.

Similar manual of arms

• Mossberg 500 / 590
• Mossberg 590A1

Legal notes

Sourcing